1. Field of the Invention
The present invention relates to movement methods, exposure methods and exposure apparatus, and device manufacturing methods, and more particularly to an exposure method and exposure apparatus that transfer a predetermined pattern onto an object in a lithography process where semiconductor devices or the like are manufactured, a movement method that can be suitably applied for moving a movable body on which the object is mounted, and a device manufacturing method that uses the exposure method and the exposure apparatus.
2. Description of the Related Art
In a lithography process to produce microdevices such as a semiconductor device or a liquid crystal display device, exposure apparatus are used that transfer a pattern formed on a mask or a reticle (hereinafter generally referred to as a ‘reticle’) via a projection optical system onto a photosensitive object such as a wafer or a glass plate whose surface is coated with a resist or the like (hereinafter generally referred to as a ‘wafer’). For example, a reduction projection exposure apparatus by a step-and-repeat method (the so-called stepper), and a scanning projection exposure apparatus by a step-and-scan method (the so-called scanning stepper (also called a scanner)), which is an improvement of the stepper, are mainly used.
Because semiconductor devices or the like are manufactured overlaying a plurality of layers of patterns on the wafer, in exposure apparatus such as the stepper, an operation (alignment) is necessary to make an optimal relative positional relation between the pattern formed in advance on the wafer and the pattern formed on the reticle. As the alignment method, the EGA (Enhanced Global Alignment) method is mainly used. The details on this method are disclosed in, Japanese Patent Application No. 61-44429 and the corresponding U.S. Pat. No. 4,780,617. In the alignment by the EGA method, a specific plurality of shot areas (also referred to as sample shot areas or alignment shot areas) in the wafer are selected in advance, and the positional information on alignment marks (sample marks) arranged in such sample shot areas is sequentially measured, and by using the measurement results and the designed array information on the shot areas, statistical calculation by the least-squares method is performed in order to obtain the array coordinates of the shot areas on the wafer. Therefore, in the alignment by the EGA method, the array coordinates of each shot area can be obtained at a high throughput, with a relatively high precision.
In the above alignment, because alignment marks arranged on a plurality of sample shot areas have to be measured, the wafer has to be moved along a path that allows the plurality of alignment marks to be sequentially positioned in the detection area of a mark detection system (alignment system) It is desirable for the movement time of the wafer for alignment to be short in order to improve the throughput, and conventionally, the movement path of the wafer was decided from the viewpoint of minimizing the total moving distance of the wafer.
However, the wafer is normally mounted on a wafer stage (biaxial-driven wafer stage) that can be driven in two axis directions that are orthogonal. In the case of such a biaxial-driven wafer stage, the movement time required for the same distance is mostly different depending on the direction in which the stage is driven. Therefore, the movement path of the wafer that has a short moving distance in total does not always necessarily match the path with a short movement time. This is because when the drive units of the two axis directions are driven simultaneously in the case of the biaxial-driven wafer stage, the sum of the drive vector decides the drive distance of the stage. Accordingly, the distance that is driven in the same period of time differs in the movement paths when only one drive unit in one axis direction is used and when both drive units are simultaneously used in the two axis directions.
In addition, recently, an exposure apparatus equipped with a stage unit using a biaxial-driven linear motor method has been proposed (for example, refer to, Japanese Patent Application Laid-open No. 2000-77301). The main focus of the proposal is to reduce the time required for step movement in between shot areas in steppers or scanning steppers, and in such an apparatus the drive axis direction is to be inclined in two axis directions, with respect to the stepping directions in between shot areas in the stepper or to the scanning and non-scanning directions in the scanning stepper.
According to the invention disclosed in the above Japanese Patent Application Laid-open No. 2000-77301, by reducing the time required for step movement in between shot areas, there is an advantage of improving the throughput. However, in the case of the exposure apparatus disclosed in the publication, for example, when considering the case of setting the stepping direction in a direction inclined at 45 degrees to a first axis direction and a second axis direction, the positional measurement error becomes 21/2 times while the time required for step movement is reduced to ½1/2. This shows that the possibility of not being able to achieve stage movement with high precision is inherent in the case of such an apparatus.